Random Access Response Beamforming Scheduling
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Solution Overview
Problem
In cellular networks employing narrow beamforming, the network entity faces challenges in determining the best downlink beam for Random-Access Response (RAR) messages due to potential mismatches between downlink and uplink beam directions, leading to inefficient resource allocation and reduced coverage.
Innovation Solution
The system successively transmits multiple RAR messages with adjustable time delay indicators in the Uplink (UL) grants, allowing for flexible scheduling and increased chances of successful reception, even when the best downlink beam is unknown, through mechanisms like many-to-one or many-to-many mappings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If narrow beamforming is employed to increase antenna gain and coverage range, then the coverage range is improved, but the angular coverage is reduced making it difficult to determine the best downlink beam for RAR messages
Solution Approach 1:
The network entity transmits multiple RAR messages in advance with different downlink beam directions before knowing which beam the UE will actually receive. This preliminary transmission of multiple beams allows the UE to select the best received message, resolving the contradiction between narrow beam gain and beam direction uncertainty.
Solution Approach 2:
The system dynamically adjusts the timing of UL transmissions based on the scheduling-delay indicator included in each RAR message. This dynamic timing adjustment allows flexible scheduling of multiple UL transmissions corresponding to multiple RAR messages, enabling the UE to respond to the best received message while maintaining efficient resource utilization.
2Reliability
If multiple RAR messages are transmitted to ensure successful reception, then the reliability is improved, but the resource allocation complexity increases
Solution Approach 1:
The network entity changes the timing parameter of UL transmissions by adjusting the scheduling-delay indicator in each RAR message. This parameter change allows multiple UL transmissions to be scheduled at different times, reducing resource allocation complexity while maintaining reliability through multiple RAR message transmissions.
Solution Approach 2:
The random access procedure is segmented into multiple independent RAR message transmissions, each with its own UL grant and scheduling-delay indicator. This segmentation allows the UE to selectively process only the RAR messages it successfully receives, reducing the complexity of resource allocation while improving reliability.
3Manufacturing precision
If the UE waits for the best downlink beam to transmit RAR messages, then the reception quality is improved, but the access delay increases
Solution Approach 1:
The network entity performs preliminary beam sweeping by transmitting multiple RAR messages with different downlink beam directions in advance. This preliminary action eliminates the need for the UE to wait for the best beam, as the best beam is already transmitted among the multiple RAR messages, thus reducing access delay while maintaining reception quality.
Solution Approach 2:
The UE provides feedback by selecting and responding to the RAR message with the best reception quality among multiple received messages. This feedback mechanism allows the UE to indicate which beam direction was most effective, enabling the network to optimize future transmissions without increasing access delay.
Data Source
AI summary
A system and method of Random-Access Response, RAR, messaging when a base station employs narrow beamforming. Multiple RAR messages are successively transmitted from the base station to a User Equipment, UE, before any response to a RAR message is received from the UE. Thus, despite any calibration mismatch between Uplink, U L, and Downlink, DL, beams in the beamformed system, a RAR message is not only received by the UE, but is received over the most-suitable DL beam for that UE. Each RAR message may contain a message-specific scheduling-delay indicator in the UL grant carried in the RAR message to provide an adjustable time delay for the UE's uplink transmission scheduled by the UL grant. Multiple RAR transmissions can schedule a single UL transmission at a specific time instance or different UL transmissions at different time intervals. The UE may report to the base station the best DL RAR transmission detected by the UE.